Muffle kiln



Patented Aug. 6, 1935 ,taf i UNITED STATES PATENT OFFICE MUFFLE KILN Frank M. Hartford, Columbus, Ohio l Application December 22, 1933, Serial No. 703,586

12 Claims. (cias-"144) 4,

This invention relates to improvements in tunvention consists in the novel features of connel kilns and has particular reference to tunnelstruction, combination of elements and arrangekilns wherein the combustion gases used in mainments of parts hereinafter fully described and taining the operating temperatures of such kilns, ,pointed out in the appended claims.

may be substantially removed fromfdirect con- 'In the accompanying drawings: l 5

tact with the ware undergoing heat treatment. Y Fig. `l is a horizontal sectional- View taken In the ring of certain ceramic products, `as through a kiln constructed in accordance with well as other heat treated products, it is often the present invention;

desirable that the combustion 'gases used in the' Fig. is l a vertical transversel sectional view .heating of the kiln be keptout of direct contact taken through a high-fire section ofV the kiln on 10 with the Ware, at least to a very appreciable exthe plane indicated by the line II-II of Fig. 1;

tent. To this end, it is an object of the present Fig, 3 is a vertical longitudinal sectional view invention to provide a tunnel kiln wherein baftakenthrough the kiln on the plane indicated fle plates are used to separate that part of the. by the line III-III of Fig. 2; n '1 5 tunnel through which the Ware passes from the Fig. 4 is adetail horizontal sectional View, the-"15 spaces on each side of the tunnel or kiln where plane of the gure being indicated by the line combustion takes place or through which the IV-IV of Fig. 2; i'

products of combustion travel towards the chargl Fig. 5 is a'detail View in side elevation of the ing end of the kiln. The result of this construcheat Iradiating panels comprising the present intion is that the heating of the Ware may be ac- Vention, the point of view of the figure being indi- 20 complished largely by radiation of heat from the cated by the line V-V of Fig. 2; surface of these baille plates onto the ware and lFig.l 6 is a detail transverse sectional View of a without any substantial direct contact with the slightly modified form of the invention. gases of combustion with the ware. Referring `more particularly to the drawings,

In the indirect fired type of continuous tunnel the numeral l designates a tunnel kiln in its en-iy25 kiln, having a stationary fire zone and moving tirety. This kiln may be formed to provide the Ware and in which the transfer of heat to the usual elongated 'wall structure shaped to proware is effected largely by radiation, one of the duce a longitudinally extending tunnel 2, coex outstanding objections thereto is `found in the. tensive with the length of the kiln. Generally,

diliculty encountered in heating the lower center the kiln. includes a preheating section, indicated 30 portion of the ware settingvto as high a tem-4 at A, a high-nre section B and a cooling section perature as the outer and top portions of theA C. It will be understood that these sections or setting. Especially is this true where the ware Zones are not separated by sharp lines of demaris being passed through such a kiln at a fairly cation but blend gradually one into the other.

rapid rate. f' The green ware to be red enters the kiln adja- 35 Where such a system of heat transfer by racent to the preheating section and emerges at da-tion to the ware is employed, there often rethe end ofthe cooling section. The kiln is thus sults a cross sectional area in the ware setting, .in .the form of ya tunnel, having vertical side around the lower central part thereof, which pos- Walls 3 3, a bottom 4 and an arched or flat roof sesses a lower temperature than the remainder of '5. The `material or ware to be heat treated. 40 the setting. In order to obviate this areay of lower passes through the tunnel on a suitable carrying temperature and more nearly heat the entire means, such as a plurality of fiat bottomed cars 6 setting equally and uniformly, the present inand moves more or lessy continuously therevention has for its primary object to provide through. The preheating and high-nre sections an improved arrangement of heat radiating bafof the tunnel are, in the kiln illustrated, of 45 fle mates between the muffle passes and the car greater width than the'cooling section. y

tunnel by which heat will be directed upwardly Starting in the high-nre section and continuand'angularly toward the lower central region of` ing throughout that section and, also, throughthe ware settings so that the ware disposed in' out the preheating section to a position close to 50 the lower .central regions of such settings will the charging end andon each side ofthe tunnel 50 receive substantially the same degree of. heat space required for the passage of ware, there is treatment by'radiation as is obtained by ware placed longitudinally aligned refractory plates disposed in other portions of such settings. l in a substantially vertical position. Usually, the With these and other objects in view,.which adjoining, vertical edges of these plates will e will appear as the description proceeds, `the in either abut or overlap, although the joints formed 55 therebetween need not necessarily be gas tight, in the sense that neither cement nor mortar need be used in joining the baille plates one with the other. These plates are indicated by the numeral 'I and are arranged on both sides of the ware tunnel to provide longitudinally extending combustion spaces S between said plates and the side Walls 3, the bottom l and the roof 5 of the kiln. Highly heated gases, such as those obtained by the combustion of fuels, pass .longitudinally through the spaces 18 from the'high-re tothe preheating ends of the kiln, thereby heating the plates l and causing the latter to radiate heat onto the ware passing through the tunnel. These high temperature gases or products of combustion are preferably introduced into thespaces t8 by means of burners 9. These burners may be disposed in upper and lowererows,.1as-'shown.in Figs. l and 2 and placed at an angle with respect to the longitudinal edges of the tunnel to pro- `rnotethe owof the-,gases throught-the spaces 8 f in the direction indicatedA bye the arrows' inrEig. :.1. .,fPreferably, the'spacesiv convergel toward the preheating end of the kiln to increase somewhatithe velocity of flow: of said .-ingend of the kilnffromwhich they iindfescape `throughthe stack outletsfzl.

In order to eifect the supportof vtheheatradiating panels orfplates '5,-the bottom-4 `of the ,-ikilnadjacent to the car pit `vIl is Vprovidedwith ledge blocks i2, composedzof a suitable-refractory material. Supported f by these :ledge a blocks .and arranged in longitudinallyvaligned contiguous relationship are a plurality of lportedrblocks i3, having the.horizontaliconguration disclosed in Fig f4. Theseablocks,'thereforeyprovide bottom walls i4 of maximum area which restdirectly upon the ledges Y|'2,and withzupperlwalls .l5 of` reduced area( asV comparedxwith; thebottom Jwalls, the walls I6: and: l5 being'united"by1integrallongitudinally spaced'vertical-postsl. The upper Y surface of Vthe'bottorn vwall iM .of each block is grooved longitudinally.contiguous :to the inner edge thereof for the; reception: of the; lower. edges of supplemental heat: radiatingv vpanels il. .These ,f panelsfhave their upper edges engaged with the --Verticallinner edges of=tl1eupperwal1s l5 soV that `by reason ofthe construction-ofthe.blocks t3; the panels r il supportedf thereby :will be disposed .in angular relationship with; respect to: the vertical. .-It will be seen that the ported iblockslcommufnicate `freelyon one side #with thercombustion spaces, and since Ithe panels Il are formed from a thin refractory: material possessing .high yheatlconductivityfthe said rpanels will radiate '.heatwat a high rate ontoithe `waresupported:in =thetunnelsfby the cars :5. Ifdesired,.-stripsal8 of a refractory f material' similar to that; used in l thef formationnof they-panelsv Vit-may beemployed to overlap thelongitudinal: meeting edges-.of the `panels Il .ftosealrthese vmeeting edge portions against tl-iepassage` of combustionigases .iniany appreciable'quantities therethrough.

-The cars1S,-whichoperate inthe pitil .are yconstructed toprovide metallic truck i frames'l carrying track engagingi'wheelsai the. frames I 9 ibeingfformedfwith depending plates 2| which are .adapt-ed to'travel in troughs22rprovided-in the 'bottom of said pit andicontaining-sand;.or other -similar heatf-sealingrmeans. The upper :portions of the frames EilV are equippedvwithitlflef.usual. re- Ifractory beds.;23, :which supportipieriblocks-M used f in r positioning the "bottom f deck 1:25 4of ythe -lrware -settinglon said f cars. Z'Ihe `.upper l.deck i is designatedrby' the 'numeral-126andsuitable .-supgases: toward the preheaty ports 21 are arranged between said decks to maintain their vertical spaced order. The ware itself is designated by the numeral 28. By virtue of this arrangement, it will be observed that the supplemental panels il' will be located below the lower deck 26, with the lower edges of the supplemental panels projecting under the deck 25. Due to the angular positions occupied by the supplemental panels, most of the heat liberated from theunder surfaces thereof 'is directedtoward the central region of `the bottom deckf25 toiheat the ware supported by said deck contiguous to that region.

The upper walls l of the blocks i3 are preferablygrooved as at 29 for the reception of the .lower rowA of panels or baiiie plates l. It will be understood that the latter may be disposed in superposed.` rows, extending from the blocks l 2 to positioning grooves Si? formed in the under sur- 'face of the roof 5. The plates Tl are arranged one *upon the otherin vertical order and in abutting :relatienshipfin: longitudinal order and are prefern .ably formed .from a thin refractory material such .ascarborundum,-asarethe plates il. A variaftionv of this structure has been disclosed in Fig. 6 fwhereinfthemanels:laextend in one piecezfroin the,bottomfl'tothe1rooffi of the kiln. In this form-of;theinvention,;the lower regions ofthe .panels 'la are. ported atti to permit of the: passage of heat directly.therethrough and into contact-.withA thesupplementalpanels lla.

fArrangedtoy rest directly on the: refractory` beds '123 ofthey cars,'are blocks 32 which.areprovided with reversely inclined: upper surfacesv 33. .These lblocks are formed from .asuitable -inaterial-and cooperate with the inclined plate' il to .direct and radiate :heat upwardly .and ceni,tr-ally. of! the fwaremass positioned upon the cars.

{What is claimed is:

l. In a continuous.muidekiln, a refractory wall `structureformedto include a bottom, side walls and-atop, said `bottom beingziorrned with a longi- .tudinally extending car ipit, imperforate heat conducting andV radiating panels spaced from said .sidewalls-,anat extendingfroni the bottom to they;

.topzoffthe kiln, and-between lwhich ware to'be ,heat treated andrsupported on cars traveling throughsaid pitiis passed, the lower portions of -saidfpanelss immediately above said bottom being ..of..reduced:thicknessand sharply inclined with respect to the vertical and arranged in horizontal .planes below that of the-.ware supported on said 'cars,f.the inclination of the inclined lower porftionsV of saidfpanels-beingsuch as to radiate heat toward the lower central portion of the ware dis- .posedonsaid cars, and burner means communicat-ing-.with'the spaces formed between said side .walls said panels.

,2. .Ina continuousmulile kiln, a heat coniining ystructureincluding'a bottom, spaced side walls ...and a roof, the bottom being formed with a cen- `trallydisposed longitudinallyfextending car pit, .transverselyspaced longitudinally extending imiperforate heat radiating walls of relatively thin Vheatconducting materialextending from said 7.bottomirorn positions contiguous to said car pit :tofthe iroof ofitheheat confining structure and separating'the'.latter interior-ly into a pair of :longitudinally extending-combustion spaces and :aan vintervening ycar tunnel, and cars movable fthrough said pit .and provided with a horizontally fdisposed'deck for the reception of ware to be heat treated, the lower portions of saidheat radiating walls being thinnerl than the upper portions and sinclinedwith lrespectltoi the Verticali touunder-lie heat insulating l said deck, whereby heat radiated from the inclined portions of said last-named walls is directed upwardly toward the central lower regions of said decks.

3. In a tunnel kiln, a heat conning wall structure of refractory materials including a bottom, spaced side walls and a roof, the bottom being formed with a longitudinally extending car pit, a plurality of ported blocks positioned on said bottom contiguous to said pit, a plurality of longitudinally aligned vertically inclined heat radiating panels supported by said blocks between their upper and lower edge portions, and thin heat conducting and radiating walls supported by the upper edge portions of said blocks and said roof,

4. In a tunnel kiln, a heat coniining structure of refractory materials including a bottom, side walls and a roof, the bottom having a longitudinally extending car pit formed centrally therein, ported blocks supported by said bottom in longitudinal rows contiguous to both sides of said pit, a plurality of superposed rows of heat radiating panels spaced from the side walls of said kiln and extending from the upper surfaces of said blocks to said roof, and supplemental heat radiating panels arranged in angular relationship with respect to the first-named panels and supported on opposite sides of said tunnel between the upper and lower edges of the ported blocks.

5. In a tunnel kiln, a heat coniining structure of refractory material including a bottom, side walls and a roof, said bottom being formed with a longitudinally extending car pit, removable walls of a heat conducting and radiating material spaced from said side walls and extending from said bottom contiguous to the opposite sides of said car pit to said roof, the lower portions of said last named walls being reduced in thickness and sharply inclined with respect to the vertical to under lie ware supported on cars travelling through the car pit.

6. In a tunnel kiln, a heat confining structure of refractory materials including a bottom, side walls and a roof, the bottom having a longitudinally extending car pit formed therein, ware-supporting cars movable lengthwise of said pit, said cars being provided with refractory bodies, means .for supporting the ware to be heat treated in the kiln from and in spaced superposed relationship with respect to said bodies, reversely inclined blocks of heat resisting material arranged on the bodies of said cars below the ware, a plurality of longitudinally aligned heat radiating panels supported between the bottom and roof of the heat confining structure and spaced from the side walls thereof, means for passing heated gases through the spaces provided between said panels and said side walls, the lower portions of said panels being arranged at an angle with respect to the vertical to direct heat radiating therefrom in an upward direction toward the central lower area of the ware positioned on said cars.

7. In a tunnel kiln, a heat conning structure of refractory material including a bottom, side walls and a roof, said bottom being formed with a longitudinally extending car pit, walls of a heat conducting and radiating material spaced from said side walls and extending from said bottom contiguous to the opposite sides of said car pit to said roof, the lower portions of said last named walls being reduced in thickness and offset with respect to the upper portion of the wall to underlie ware supported on cars traveling through the car pit.

8. In a muffie kiln, a heat conning structure of refractory material including a bottom, side walls and a roof, said bottom being formed with a 1ongitudinally extending car pit, substantially vertically extending heat conducting and radiating plates spaced from the side walls and bottom Walls, and downwardly and inwardly inclined panels arranged between said plates and said bottom.

9. In a muiie kiln, a heat confining structure of refractory material including a bottom, side walls and a roof said bottom being formed with a longitudinally extending car pit, heat conducting and radiating plates spaced from the side walls and extending from the roof downwardly to a point spaced from the bottom of the kiln, and thin panels provided to bridge the space between the lower ends of the plates and the bottom.

10. In a muflle kiln, a heat confining structure including a bottom, side Walls and a roof, said bottom being formed with a longitudinally extending car pit, vertically extending heat conducting and radiating plates spaced from said side walls and engaging said bottom and roof to provide a cornbustion chamber on either side of said oar pit, and thin downwardly and inwardly inclined panels offset with respect to said plates and directly contacted by the products of combustion in said chambers.

1l. In a muflle kiln, a heat conning structure including a roof, side walls and a bottom, said bottom being formed with a longitudinally extending car pit, heat conducting and radiating plates arranged between said bottom and roof and spaced from said side walls to provide a combustion chamber on either side of said car pit, and thin inclined panels arranged at the edge of said car pit and directly contacted by the gases of combustion in said chambers.

l2. In a muie kiln, a heat conning structure including a roof, side walls and a bottom, said bottom being formed with a longitudinally extending car pit, baffle plates of heat conducting and radiating material extending between said bottom and roof and spaced from said side walls to form a combustion chamber on either side of said car pit, said baffle plates being formed with openings near their lower edges, and thin inclined panels arranged between said plates and the edge of said car pit and covering said openings to prevent escape of combustion products from said chambers.

FRANK M. HARTFORD. 

